This invention relates to apparatus for tensioning safety belts and in particular to such apparatus as are activated by the displacement of a piston in a working cylinder resulting from the application of gas pressure.
Prior art safety belt tightening devices, such as disclosed by Schwanz et al. in U.S. Pat. No. 3,871,470, make use of a piston in a working cylinder which is responsive to applied gas pressure to take up slack in a safety belt in the event of a vehicle accident. Such devices are useful in vehicles which have sensors for detecting the occurence of a vehicle accident. Such sensors may detect a collision by a device projecting from the front of the vehicle, or may respond to a rapid deceleration of the vehicle. Upon the occurrence of a vehicle accident, a signal discharges a pyrotechnic device or applies gas pressure in some other way to cause displacement of the piston. The apparatus disclosed by Schwanz makes use of the motion of the piston to draw the safety belt between a pair of support members thereby taking up slack in the belt. The prior art device additionally include a locking device to prevent reverse motion of the piston in the cylinder after completion of the tensioning movement.
While the prior art device is effective in tensioning a safety belt on the occurrence of an accident, it is usually arranged separate from and in addition to a safety belt winding device, and therefore requires a separate installation operation and takes up additional room within the vehicle.
It is therefore an object of the present invention to provide an apparatus for tensioning a safety belt on the occurrence of an accident, which apparatus is incorporated onto a belt winding device.
It is a further object of the present invention to provide such an apparatus within the smallest possible structure.